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Fuel gauge and tachometer gauge not working properly?

Tiny
ROADNINJA73
  • MEMBER
  • 2005 PONTIAC AZTEK
  • 4 CYL
  • 2WD
  • AUTOMATIC
  • 115,000 MILES
I just bought my car, I love it. But, I have an issue I need help with. When I first drove my car, I noticed the fuel gauge was stuck below empty.
I stopped and put gas in it. The fuel gauge didn't move until maybe after driving twenty miles. Then it jumped way up past half. My tachometer was stuck as well. The lot mechanic mentioned he had just changed the relay and it seemed a tad loose. So he bent the prongs out and it worked. Could this be the problem? Any help would be very much appreciated. I love this car otherwise! Thank you!
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Friday, April 5th, 2019 AT 5:28 AM

19 Replies

Tiny
SCGRANTURISMO
  • MECHANIC
  • 4,897 POSTS
Hello,

The fuel gauge is a float that rides on a metal rod in your fuel tank. Over time the rod gets gunked up with stuff from the fuel and the float will no longer be able to move up the rod when you put fuel in your fuel tank. The best way to fix this is to replace the fuel sending unit altogether. The tachometer gets it's signal from the Power-train Control Module (PCM) which gets it's signal from the Vehicle Speed Sensor (VSS) which is on your vehicle's trans-axle.
I have included in the diagrams down below location, test, and removal and installation instructions for both the VSS and Fuel Sending Unit. Go through this information and get back to us with what you find out. The tests will have you use a multi-meter, so if you are unfamiliar with how to use one a have included a link below for you to go to if needed.

https://www.2carpros.com/articles/how-to-use-a-voltmeter

Thanks,
Alex
2CarPros
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Friday, April 5th, 2019 AT 7:26 AM
Tiny
GRIZ5901
  • MEMBER
  • 2 POSTS
  • 2005 PONTIAC AZTEK
  • 50,000 MILES
It litterally gets stuck over n the gas gauges side. N its not overheating.
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Monday, August 24th, 2020 AT 12:10 PM (Merged)
Tiny
ASEMASTER6371
  • MECHANIC
  • 52,797 POSTS
It could be failed gauge unit. A shop with a scan tool can manipulate the cluster to verify a failure.

Roy
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Monday, August 24th, 2020 AT 12:10 PM (Merged)
Tiny
GRIZ5901
  • MEMBER
  • 2 POSTS
What kind of scan tool can manipulate the cluster.
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Monday, August 24th, 2020 AT 12:10 PM (Merged)
Tiny
04AZTEK
  • MEMBER
  • 1 POST
  • 2004 PONTIAC AZTEK
  • 79,000 MILES
My fuel gauge has always been sketchy when under a quarter tank. So I leave it full. Recently my temp gauge has been in red red red! I took it to mechanic and he said fan is fine but sensor was replaced and he said the gauges are not working properly and I should try dealer to reset. Worked fine all weekend and now temp is above red and gas gauge is above full after driving 140 miles. What should I do next? Help!
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Monday, August 24th, 2020 AT 12:10 PM (Merged)
Tiny
HMAC300
  • MECHANIC
  • 48,601 POSTS
It may be the dash has gone bad as they are digital. They can be rebuilt just make sure everything is ok like coolant temp etc. You can look online of rebuilders.
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Monday, August 24th, 2020 AT 12:10 PM (Merged)
Tiny
MISFIT163
  • MEMBER
  • 1 POST
  • 2003 PONTIAC AZTEK
  • 3.4L
  • 6 CYL
  • AUTOMATIC
  • 198,000 MILES
Fuel gauge stays on full when switch is on.
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Monday, August 24th, 2020 AT 12:10 PM (Merged)
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 109,747 POSTS
Hi and thanks for using 2CarPros. Com.

The fuel gauge operates off a sending unit and float in the fuel tank. Often times, the sending unit, which uses a rheostat to send signals to the gauge, fails. Basically, the rheostat fails and needs replaced.

To properly test the system requires a good bit of time and proper tooling. I am going to attach 4 pictures which are the diagnostic flow chart needed to test for the fault. Here are the directions.

FUEL GAGE INACCURATE OR INOPERATIVE

DIAGNOSTIC AIDS
- Ensure that the fuel level is in the same range as the customer concern.
- Refer to Fuel Level Specifications in order to verify the correct fuel level sender readings. The Fuel Level (%) parameter is available on the scan tool in the PCM EVAP data list.

TEST DESCRIPTION
See attached pictures for procedures.
_____________________________________

Let me know if this helps or if you have other questions. I realize it is quite involved.

Take care,
Joe
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Monday, August 24th, 2020 AT 12:10 PM (Merged)
Tiny
PUNKYKID3
  • MEMBER
  • 1 POST
  • 2003 PONTIAC AZTEK
  • 6 CYL
  • AWD
  • AUTOMATIC
  • 109,000 MILES
I recently had the fuel pump replaced. Today the fuel guage has been very erratic. First it says empty and the low fuel light comes on, then it reads full. Would it have anything to do with the pump being replaced?
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Monday, August 24th, 2020 AT 12:11 PM (Merged)
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 109,747 POSTS
The float in the fuel tank is what sends the signal to the gauge. It is part of the fuel pump. Therefore, yes, the new pump / float assembly could be faulty.
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Monday, August 24th, 2020 AT 12:11 PM (Merged)
Tiny
TINAG121468
  • MEMBER
  • 1 POST
  • 2003 PONTIAC AZTEK
Engine Mechanical problem
2003 Pontiac Aztek 6 cyl Front Wheel Drive Automatic

all just happened in last 2 days. 1. Fuel gauge goes from full to empty back to full than to where I think may be correct. 2. Idles at 3 on RPM 3. Isn't shifting correctly 4. Turn key on only to turn radio on and all gauges go crazy
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Monday, August 24th, 2020 AT 12:11 PM (Merged)
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 109,747 POSTS
Hi:
It sounds like there may be a problem with the body control module (BCM). Try disconnecting the battery for around 5 minutes the reconnect. This should reset it if that is the problem. Let me know if it works or if you have other questions.

Joe
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Monday, August 24th, 2020 AT 12:11 PM (Merged)
Tiny
KSPENCER29
  • MEMBER
  • 1 POST
  • 2002 PONTIAC AZTEK
  • 6 CYL
  • AWD
  • AUTOMATIC
  • 105,000 MILES
My daughters Aztek gas gauge will show the correct amount when started but will show empty moments later. Any thoughts?

Her AWD disable light comes on frequently also.
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Monday, August 24th, 2020 AT 12:11 PM (Merged)
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 109,747 POSTS
Hi:
It sounds like the rheostat is bad on the fuel float. It is part of the fuel pump in the fuel tank. The tank needs removed to check and replace it. As far as the AWD light, have the computer scanned at a nationally recognized parts store. Most will do it for free and it will help identify the problem.

Joe
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Monday, August 24th, 2020 AT 12:11 PM (Merged)
Tiny
BRIJMIN
  • MEMBER
  • 11 POSTS
  • 2002 PONTIAC AZTEK
  • 150,000 MILES
The Aztek has been running like a champ. No problems what so ever. During the last cold snap in Michigan the fuel gauge started working a little funny. Like reading too much gas (more than expected) or too little gas (less then expected) but it would eventually read right once the car got warm. That lasted 2 or 3 days. Now the gauge goes from full to empty in a flash.

Now I use the mileage trip to tell how much gas I have. No problem in the short term.

Now the question.

Is this because of the fuel level sensor? Do they tend to fail quickly like that?

I understand this is a common problem, but I thought they lingered for a while before totally failing. I understand the brushes that make the contact to the float tend to ware out and cause the gauge to mis-read, like not all the way full or not empty.

The way this one failed leads me to the question. Is this normal?
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Monday, August 24th, 2020 AT 12:11 PM (Merged)
Tiny
ALKIMBALL
  • MEMBER
  • 1 POST
I am having the same problem with my fuel gauge. It goes from full to empty in 5seconds. Its so annoying and I would love to find a solution for my problem.
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Monday, August 24th, 2020 AT 12:11 PM (Merged)
Tiny
BRIJMIN
  • MEMBER
  • 11 POSTS
I have been told this is a common problem. The auto supply store will sell you the entire pump and float assembly for about 300 bucks. I have been told to go to the local GM dealer and ask for just the float assembly. It will be much cheaper.
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Monday, August 24th, 2020 AT 12:11 PM (Merged)
Tiny
TMKNIPE4
  • MEMBER
  • 1 POST
  • 2001 PONTIAC AZTEK
  • 6 CYL
  • FWD
  • AUTOMATIC
  • 120,000 MILES
My fuel gauge "floats" when it gets around half a tank
never really know how much fuel there is told a modulator on the fuel pump controls this can this part be replaced alone or does the pump itself need to be replace where can I get diagrams for where and how to fix this problem
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Monday, August 24th, 2020 AT 12:11 PM (Merged)
Tiny
RASMATAZ
  • MECHANIC
  • 75,992 POSTS
FUEL LEVEL SENSOR REPLACEMENT

REMOVAL PROCEDURE


https://www.2carpros.com/forum/automotive_pictures/12900_fs1_1.jpg



Remove the fuel sender assembly.
Disconnect the fuel pump electrical connector (2).
Remove the fuel level sensor electrical connector retaining clip (4).
Disconnect the fuel level sensor electrical connector from under the fuel sender cover (5).
Remove the fuel level sensor retaining clip.
Squeeze the locking tangs and remove the fuel level sensor (3) from the modular fuel sender.

INSTALLATION PROCEDURE


https://www.2carpros.com/forum/automotive_pictures/12900_fs1_1.jpg



Install the fuel level sensor (3) to the modular fuel sender.
Install the fuel level sensor retaining clip.
Connect the fuel level sensor electrical connector.
Install the fuel level sensor electrical connector retaining clip (4).
Connect the fuel pump electrical connector (2).
Install the fuel sender assembly
Inspect for fuel leaks with the following procedure:
7.1. Turn ON the ignition for 2 seconds .
7.2. Turn OFF the ignition for 10 seconds .
7.3. Turn ON the ignition.
7.4. Inspect for fuel leaks.

https://www.2carpros.com/kpages/auto_repair_manuals_alldata.htm
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Monday, August 24th, 2020 AT 12:11 PM (Merged)

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